Last summer, my friend Sian was threatened with arrest for having a picnic in Parliament Square. The police had said her meal was a political demonstration, as she had the word "Peace" iced on a cake. Under the Serious Organised Crime and Police Act (Socpa), which restricts the right to demonstrate near the square, she should have got permission from the police six days before getting the victoria sponge out of its Tupperware container. As the law insists that one person counts as a demonstration, anyone wearing a CND, trade union or Vote Conservative badge in Parliament Square could, in theory, be arrested for demonstrating without permission.

Most people know that this rule was brought in by Labour to kick the peace campaigner Brian Haw out of Parliament Square. What many do not know is that it does not just apply to the square, but to a designated zone covering a sizable part of central London. So if you wanted to stand outside the Channel 4 building, 10 minutes' walk away from the square, with a badge saying "Please don't repeat Friends any more", you would need police permission.

While some have chosen to challenge the law by noncompliance - such as Maya Evans, who was arrested and fined last December for reading out the names of those killed in the Iraq war by the Cenotaph - others have chosen a less confrontational approach. If the police need to issue licences for each and every lone demonstrator, they said to themselves, what would happen when a whole load of lone demonstrators arrive at the same time for individual permissions to demonstrate? So, the past three months have seen mass lone protests, in which about 150 people test police bureaucracy by getting licences for each and every one of them. The police can only refuse to issue the licences on the grounds of public safety or public order

Inspired by these mass actions, I decided that I would demonstrate all over the Socpa zone - and, being an upright citizen, get permission to do it. So, last week, I nipped into Charing Cross police station to apply to have 21 individual demonstrations on the same day in the designated area.

Through earlier protests, I have got to know the man who coordinates the requests quite well. PC Paul McInally now handles most of the Socpa applications. "What can I do for you today, Mark?" he asks, as we sit in the interview room.

"I've got 21 forms for you."

"Right then," he says in a businesslike fashion, "let's go through them." I like PC McInally. We sort of bonded a few months ago when I handed in an application to demand the immediate sacking of Superintendent Terry.

"You want to sack my direct superior!" PC McInally had spluttered.

"Yes, please."

"I've got to go and ask him if you can have a demonstration calling for him to be sacked?"

"I believe so." I said. And although he shook his head when he left the room, he was smiling.

The area covered by Socpa is covered by several police stations, and now PC McInally sat flicking through the 21 forms sorting out which would deal with which request. "This one is on the Belgravia patch; so is this one. Ah . . ." he pauses, "this one is Parks police."

All in all, four police groups are needed to give me the permission I need: Charing Cross, Belgravia, Lambeth and the Parks police.

Nick Woodward from Belgravia gets in contact about the demos on his "patch". He is altogether a different type of officer - he handles a moustache like he fought in the Battle of Britain and sports Coldstream Guards cufflinks. If Terry-Thomas had ever joined the Nazis, he would behave a little like Woodward. "Mark, Nick Woodward," he bays down the phone.

"Hi, how are you?"

"I'm well, thank you," he says. "Though I am a little disappointed that you have decided to waste our time in this manner. I've now got to open eight separate files on this."

"As you know, I am very concerned about these issues," I tell him. "As you can see, my first demonstration is to reduce police paperwork."

"Yesss," says Nick. But I know he really wants to say, "You're a bloody shower."

But permission is given, and this Monday I set off with the aim of doing 21 demonstrations in the Socpa zone in five hours and 15 minutes. Each demonstration would be 10 minutes long, with five minutes travelling time between them. The police agreed that I could have two assistants to keep time, check the route and carry the banners.

Sam is the banner caddy. Originally we wanted to use a golf bag to carry the placards. "Ah, Downing Street, sir," he would have respectfully intoned. "You'll need a 'Hang Blair Banner'." Unfortunately, we don't know anyone with a golf bag, so I recondition my wheelie bin to carry the placards. Tony is my timer and route checker.

And this is how I do ...

10am, Parliament Square: Demonstration to Reduce Police Paperwork

The place is swarming with cops who have turned up to police the unapproved Sack Parliament demonstration. On arrival in Parliament Square, we are all promptly photographed by the Forward Intelligence Team for police files. Big Ben strikes 10 and up the banner goes.

10.15am, Portcullis House (MPs' offices): Demand that MPs Don't Take Other Jobs - One is Enough!

We arrive two minutes early and the timer insists we keep the banner face down until we are officially allowed to start. A line of police officers face us. Tony the timer counts me in "Three, two, one, demonstrate!"

New police arrive, shoving warning notices into our hands about unlawful demonstrations. The cops who have been standing opposite us remonstrate with their newly arrived colleagues. "They've got permission, they're OK."

The new cops look confused and Sam opens the lid of the wheelie bin, where we have stuck copies of our police approval to the inside of the lid. The police peer into the wheelie bin, and say, "Right. OK then." And skulk off.

10.30am, Tattershall Castle pub boat at the Embankment: Demonstration to demand that Pub Boats Give us Fishing Rights off the Bows or Give us Death!

10.45am, Hungerford Bridge: Demonstration to demand Trolls for London Bridges

Stopped by the police, who check permission. Cross the bridge shouting, "We need trolls! We are overrun with goats! These goats coming over here, stealing our jobs, getting the best houses! It wouldn't happen if we had trolls. And I bet they would keep the underside clear of dead Italian bankers, too." I really should get a proper job.

11am, Jubilee Gardens: Demonstration to Ban Static Mimes

Those mimes who dress up and paint themselves silver and then stand still for money - what is the point of a mime that does not move? To me, this is just an advanced form of begging. I sit immobile with a hat in front of me. No one puts any money in. I must have twitched and spoiled the purity of the moment.

The old GLC building, County Hall, was sold to a private consortium by Mrs Thatcher et al and is now private property. So I spoke with the landowners to try to get permission. "We don't allow demonstrations," said a clipped voice. "This is private property."

"By the Thames embankment?"

"Yes, we own it and security will ask you to leave."

Security are on the lookout on the day, but I sneak under the radar with a small unapproved banner. Sian arrives with tea and a cake; this one has "Stop The Killer Rays!" iced on it. We eat our cake in illegal protest pleasure.

11.30am, St Thomas' Hospital: How are you going to stop MRSA when the soap dispensers in the gents were bust last week?

Just a quick one here, as time is tight.

11.45am, MI5 Building: Give MI5 a Nameplate

MI5 has no sign outside of it saying it is MI5, and I am convinced that they are not getting all of their post.

12 noon, Magistrates Court: Demand that Judges Wear Clown Wigs

Neil Goodwin is up before the judge today; his crime is dressing as Charlie Chaplin and standing in front of Downing Street with a sign saying "Not Allowed". He was arrested for demonstrating without permission. He pleads guilty and is given a conditional discharge.

12.15pm, Channel 4: Big Brother is Shit

PC McInally had said, "What about the three nuns and the schoolkids who walk past? They could find the wording offensive." So I take a covering banner just in case. Sam and Tony are to shout "Nun!" if they see anyone likely to take offence and I will cover the offending word with a banner saying "Not Very Good."

After I have been shouting up at their offices for a bit, someone from the institute appears and says, "It's the Adam Smith International Institute that gets all the DFID [Department for International Development] government work - different organisation."

Shout "Sorry" to the three floors of office workers who are now looking out the window, scrape dignity off floor and go!

12.45pm, Department of Trade and Industry: Stop the Export of Torture Equipment

Self-explanatory.

1pm, New Scotland Yard: Sack Blair as Commissioner, Replace Him with PC McInally

Very popular choice as a lot of passing cops smile in support. Do a quick interview with Channel 4 News. "Don't the government need this law in times like this?" they ask. "Are you implying that this law will help fight terrorism?"

"Yes."

"If all that stands between us and a terrorist attack is a licence from the police, we are all doomed," I reply.

Kongra Gel is a Kurdish organisation which the EU and UK have wrongly claimed is a terrorist group. Nick Woodward warned me that I could get arrested if I do anything to support Kongra Gel, as this would break the anti-terror law. Cunningly, my slogans are in Kurdish, which means he will have to get them translated to check.

"What are you demonstrating about?" grumbles a rather fierce-looking elderly gent with glasses and a frown that suggests he once worked in a prep school. I hold up the banner."Oh, I quite agree. She's awful," he says before getting on a red omnibus home.

3pm, Parliament Square: Make Protesting Mandatory

The square is full of police, whose massed fluorescent jackets hurt the eyes and prob- ably breach EU light-pollution regulations. On Whitehall, the police explain that although I am allowed to demonstrate in Parliament Square, because the police are still arresting folk from the anti-war demonstration, there might be difficulty.

The cop in charge arrives. "Right then, I am assigning these two officers to you. They will escort you into the square, find a bit of it that isn't in the thick of the melee, and make sure you can legally demonstrate without getting any hassle from any of the other cops."

With that, I am given my own personal escort through a landscape of cops and protestors. They walk either side of me; I feel like the Noël Coward of protestors - "Demonstrating without a personal police escort? Simply not done this season, old boy." A surreal end to a surreal day. However, I have now set the record: 21 demonstrations in five hours and 15 minutes in the Socpa zone. Anyone care to try to beat it?

· Mass lone demonstrations are held every third Wednesday of every month in Parliament Square. Application forms to demonstrate on www.markthomasinfo.com